The present invention relates to a method and an apparatus for electrolyzing zinc.
In a conventional method for electrolying zinc, electrolysis is carried out in such an electrolytic cell 2 as shown in FIG. 1 to deposit the zinc into an Al plate 1. The cell 2 consists of the Al plate 1 functioning as a cathode which is vertically disposed and immersed in electrolyte 3, and a Pb-Ag (1 weight %) plate 4 functioning as an anode which is vertically disposed and immersed in the electrolyte 3 so as to be opposed to the al plate 1.
In the above method for electrolyzing zinc, however, the oxygen overvoltage of oxygen evolved on the Pb-Ag plate 4 is high, and the electric current is difficult to flow due to the oxygen bubbles. Therefore, the rate of the electrolysis is so slow that it requires a long time to electrolytically deposit the zinc 5 onto the Al plate 1. Further, since the peel-off of the zinc 5 from the Al plate 1 is required every 40 hours or more, the efficiency is quite poor. Since, moreover, the Al plate 1 must be pulled up from the electrolyte 3 on all such occasions, the working efficiency is quite poor.
When, in order to overcome these disadvantages, the voltage is elevated to accelerate the electrolysis rate, the cell voltage rises due to the electrolyte resistance, and further the temperature of the electrolyte 3 rises to require large power consumption to that extent. When the resistance between the electrodes is lowered by making the inter-electrode distance smaller, the volume of the oxygen bubbles in the electrolyte 3 evolved on the Pb-Ag plate 4 remarkably increases because the oxygen bubbles are difficult to pass through so that the electric current is more difficult to flow. When, in such conditions, the oxygen evolved on the anode and the hydrogen evolved on the cathode are tried to be separately taken out, it is difficult to accomplish it because the oxygen and the hydrogen are likely to be mixed.
Moreover, in the conventional method for electrolyzing zinc, transition metals are likely to be contained in an electrolytic bath which evolve hydrogen and decrease the current efficiency. Therefore, the zinc electrolysis is generally conducted in the clean bath after dummy electrolysis is performed to eliminate the transition metals. However, this method of electrolysis is insufficient to obtain a satisfactory current efficiency because the hydrogen is likely to evolve when the current density is increased.